STIs are infections which are spread from person to person during sex – including oral sex and anal sex.
Injection drug use, tattooing or body piercing can also spread an infection if the needles and equipment aren’t clean. An STI can sometimes be passed from a mother to her baby during pregnancy, at the time of delivery and through the process of breastfeeding.
STIs can infect you in many ways. They can be caused by bacteria. They can be viruses. They can even come in the form of parasites like pubic lice. STIs are found on the body, in blood and in body fluids like semen and vaginal fluids. Sometimes, STIs like genital warts and herpes can be spread through skin-to-skin contact.
Most STIs can be cured, but some will never go away and may require lifelong treatment.